Bactericidal action of photoirradiated gallic acid via reactive oxygen species formation

Keisuke Nakamura, Yasutomo Yamada, Hiroyo Ikai, Taro Kanno, Keiichi Sasaki, Yoshimi Niwano

Research output: Contribution to journalArticlepeer-review

83 Citations (Scopus)


It is known that gallic acid shows antimicrobial activity. In the present study, photoirradiation induced reactive oxygen species formation was investigated for augmentation of the antimicrobial activity of gallic acid. Staphylococcus aureus suspended in 4 mmol/L gallic acid was exposed to blue light of a LED at 400 nm. This treatment killed the bacteria, and a >5-log reduction of the viable counts was observed within 15 min. By contrast, neither the LED treatment alone nor the treatment with gallic acid alone showed substantial bactericidal effect. When hydroxyl radical scavengers were added to the suspension, the bactericidal effect of photoirradiated gallic acid was attenuated. Furthermore, electron spin resonance analysis demonstrated that hydroxyl radicals were generated by the photoirradiation of gallic acid. Thus, the present study suggests that the photo-oxidation can enhance the antimicrobial activity of gallic acid via hydroxyl radical formation.

Original languageEnglish
Pages (from-to)10048-10054
Number of pages7
JournalJournal of Agricultural and Food Chemistry
Issue number40
Publication statusPublished - 2012 Oct 10


  • bactericidal action
  • gallic acid
  • hydrogen peroxide
  • hydroxyl radical
  • photo-oxidation


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